Glad you had a good time. What forces did you play? Campaign or just a one off?
Answers below:
1) use of cover and peeking
when a firefight happens, do both sides initially define who is peeking
else it looks strange that I fire and then my opponent can come out of hiding and fire with guys I couldn't fire at
ANSWER:
By default, the enemy decides to peek after you have fired. The catch is that the ones that pop up cannot act in their next turn as they were "committed" during the firefight.
If that still doesn't work you, declaring peeking first is likely to be fine too. I imagine it'd play fine either way.
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2) in cases like flinch or bail.. do you need to move the full distance or only up to the spot where you can get into hiding?
ANSWER:
Flinch is into cover. So if you roll a 4 but cover is 2" away, just move him there.
Bail right now is the full move, though I may tweak that. The way I play it is to look at what spots of cover are about 12" behind them and away from the enemy that forced the Bail.
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3) recovering from results such as knocked down, does that take one of my "two activations" ? can it be done with scurry ? do they recover and act or do they recover and have to wait for the next activation to act ?
ANSWER: Recovering counts as an action but if the guy recovers, he also gets to act normally.
Basically it goes "activate this guy, roll for recovery, move and fire if he recovers".
I exclude them from scurries and fire fights, though I could see an argument for letting them recover but not actually act on those.
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4) minis have 180 degrees for line of sight, does turning to face trigger guard fire? Does it trigger the 4" i ch snap fire? I guess not since te figure turning was not actually out of line of sight, correct?
ANSWER: Turning in place doesn't count as movement and no, it won't trigger any fire.
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5) if is my turn firefight, do flinch results take effect before the opponent minis take part in the firefight or is it all assumed to be simultaneous?
ANSWER: Flinching occurs first so it may take enemies out of the firefight if they weren't in cover.
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6) I'm not sure how to use the scenarios/missions for pick up games, does one side roll on forces table and the other gets the enemies or do they each roll on forces tables and roll different missions?
ANSWER:
If you are just doing a one-off but still want to use a mission, one player is "the enemy". Since the game goes pretty quick, you can swap afterwards.
Hope that helps!